1. Field of the Invention
The present invention relates to a portable pressure monitor with a disposable cathether, in general, and to a universal physiologic pressure monitor finding particular application in the monitoring of compartment syndrome, in particular.
2. Background of the Prior Art
A compartment syndrome results from increased tissue pressure in a closed fascial space or compartment of the human body. A detailed overview of compartmental syndrome is presented in an article entitled, "Compartmental Syndrome: a Unified Concept," by Dr. Frederick A. Matsen, III, Clinical Orthopaedics and Related Research, Number 113, November-December, 1975, pages 9-13. This increased tissue pressure can adversely affect the circulation to the nerves and muscles within the involved compartment, ultimately leading to the death of those tissues. Tibial fractures and severe contusions are the most common causes of compartment syndrome. Besides these, there are a great number of additional problems which can cause the syndrome. Among these are drug overdose with limb compression, third degree burns, arterial occlusion with post-ischemic swelling. Finally, vigorous exercise can also contribute to compartment syndrome.
In the initial stages of compartment syndrome, the primary injury causes hemorrhage, edema, or both, in the closed fascial compartment of the extremities of the person who has been injured. The natural course of an untreated compartment syndrome may be devastating and can result in muscle contracture and neural deficiency known as Volkmann contracture. Some additional names given to some of the conditions in which compartmental syndrome plays a central role are as follows: Volkmann's ischemia; Compartment syndrome; Impending ischemic contracture; Rhabdomyolysis; Crush syndrome; Exercise ischemia; Local ischemia; Traumatic tension ischemia in muscles; Acute ischemic infarction; Ischemic necrosis; Anterior tibial syndrome; Peroneal nerve palsy; Calf hypertension; amd Phlegmasia cerulea dolens.
Thus, the control of pressure build-up within a muscular compartment in order to prevent nerve and muscle damage is recognized in the prior art and certain prior art techniques employing a Sorensen wick catheter in conjunction with manometer are known. However, these techniques are quite time consuming. Further, the bulky size of known pressure monitors prevents their use in all areas of a hospital.
In measuring the pressure within a fascial space, under the prior art technique, a Sorensen wick catheter is inserted within the fascial space and the other end of the catheter is secured to a large pressure monitor that includes a manometer. The wick catheter technique was developed in 1968 for measurement of subcutaneous pressure. In this regard, see "The Wick Catheter Technique for Measurement of Intramuscular Pressure" by Dr. S. J. Mubarak et al, The Journal of Bone and Joint Surgery, Vol. 58-A, No. 7, October 1976, pp. 1016-1020. Also see "A Model Compartmental Syndrome in Man with Particular Reference to the Quantification of Nerve Function," by Dr. Frederick A. Matsen, III, et al, The Journal of Bone and Joint Surgery, Vol. 59-A, No. 5, July 1977, pp. 648-653. The pressure generated within the fascial space is directly proportional to the mass of the fluid within the manometer multiplied by the gravitational constant and further multiplied by the height difference between the location of the fascial space and the location of the pressure transducer associated with the pressure monitor. Therefore, relative height changes between the location of the wick catheter and the pressure transducer can create a hydrostatic pressure head which effects the readout accuracy of the pressure monitor. For this reason, such monitors must possess complex zeroing circuitry in order to insure that when there is a height difference between the location of the fascial space being monitored and the pressure transducer there is full compensation for the developed hydrostatic pressure.
Thus, there is a need for a portable, low-cost pressure monitor which can easily monitor the pressure build-up within a muscle compartment and, when a dangerous condition exists within the compartment, to notify medical personnel of the condition. The present invention is directed toward filling that need.